Chipping apparatus

ABSTRACT

Pieces of scrap veneer are fed by a conveyor belt across an anvil and into a rotating chipper head. The pieces are held against the anvil by a plurality of laterally spaced pivotal fingers having wide flat tip portions overlying the anvil. An inflatable air bag extends over the fingers and underneath a pivotally supported adjustable weight member for resiliently urging the finger tip portions against the anvil. When the tip portion of one or more of the fingers rises to a predetermined height, the weight member is lifted with the finger so that the holddown force on the veneer does not exceed a predetermined maximum limit.

United States Patent 1 Plough 1 Feb. 27, 1973 [54] CHIPPING APPARATUS [75] Inventor: Irving L. Plough, Everett, Wash.

[73] Assignee: The Black Clawson Hamilton, Ohio [22] Filed: April 7, 1971 [21] App1.No.: 131,870

Company,

[52] US. Cl. ..144/242 R, 144/249 [51] Int. Cl ..B27b 31/00, B271 11/00 [58] Field of Search... 144/162, 163, 176, 242 A, 242

[56] References Cited UNITED STATES PATENTS 3,335,771 8/1967 Ledergerber ..144/242 R 749,072 1/1904 Marsh ..144/243 10/1951 Elmendorf ..241/92 X 7/1956 Fish et al. ..144/242 R [57] ABSTRACT Pieces of scrap veneer are fed by a conveyor belt across an anvil and into a rotating chipper head. The pieces are held against the anvil by a plurality of laterally spaced pivotal fingers having wide flat tip portions overlying the anvil. An inflatable air bag ex tends over the fingers and underneath a pivotally supported adjustable weight member for resiliently urging the finger tip portions against the anvil. When the tip portion of one or more of the fingers rises to a predetermined height, the weight member is lifted with the finger so that the holddown force on the veneer does not exceed a predetermined maximum limit.

8 Clalms, 4 Drawlng Figures PATENTED FEB 2 71973 INVENTOR IRVING L. PLOUGH nrro /vsrs CHIPPING APPARATUS BACKGROUND OF THE INVENTION In a wood chipping machine of the type generally disclosed in Fish et al. U.S. Pat. No. 2,756,788 which is assigned to the assignee of the present invention, multiple layers or mats of scrap veneer or other wood pieces are fed into a rotating chipping head by an endless belt conveyor which extends to an anvil positioned adjacent the path of the knives on the head. The mats of veneer are commonly received in surges by the chipper and held against the conveyor by a segmented driven press or holddown roll supported by a pivotable frame. The press roll has axially spaced grooves through which extend a plurality of laterally spaced rod-like fingers having tip portions which hold the veneer pieces against the anvil. The fingers are pivotally supported by the pivotable frame supporting the driven holddown roll so that the holddown roll and fingers can accommodate mats of veneer of various thicknesses.

It has been determined through the use of high speed photography that when a mat of veneer pieces, for example, of one inch thickness or greater, is fed into the path of the chipping knives, the holddown fingers are subject to extreme elastic rebound following the cutting action of each knife. This rebound of the fingers is caused by the sheets of veneer being pressed tightly together during the cutting operation due to the pinching action between the knife and the anvil. When a cut is completed, the veneer rebounds to a height of one and one-half to two times the normal height of the stack of the veneer.

As a result of this rebounding and the rapid slapping action of the veneer against the fingers, thev fingers are elevated to normal operating positions which are about one inch or more above the normal height of the veneer mat. The slapping action against the fingers also frequently causes the uppermost veneer sheets in the mat to be split along the grain, and some of the split fragments upend and pass downwardly between the anvil and the chipping knives, thereby producing overlength chips which are undesirable for use in producing pulp or particle board. The fluttering of the veneer also produces small cracks within the upper sheets of veneer, and the chips cut from these sheets, contain a high percentage of narrow slivers or pin chips.

SUMMARY OF THE INVENTION The present invention is directed to a veneer chipper feedworks as generally disclosed in the above patent and which incorporates an improved mechanism for holding the veneer sheets against the feed conveyor and against the anvil between successive cuts of the chipper knives. Thus the mechanism of the invention significantly reduces the rebound of the veneer sheets so that the overlength chips and the pin chips are substantially eliminated. In addition, the holddown mechanism of the invention is highly durable so that it can receive large feed surges of material over an extended period of operation and require only the minimum of maintenance. The mechanism also does not incorporate any components such as nuts, bolts or other small parts which are likely to break off and be fed into the chipper.

In accordance with one embodiment of the invention, a holddown mechanism incorporates a plurality of laterally spaced pivotal fingers each of which has a broad flat tip portion overlying the anvil. An air bag extends laterally across the top of the fingers and underneath a weight member which is supported for pivotal movement about the pivot axis of the fingers. The pressure within the air bag and the value of the weight member can be selected to minimize the rebound effect of the fingers and to control the max imum force exerted downwardly by the fingers on the veneer sheets. The mechanism of the invention also incorporates a holddown or press roll which is segmented to receive the interfitting fingers and which incorporates resilient rubber-like axially extending ribs on its outer surface to reduce the high shock loads on the veneer mats being fed across the anvil and then to the chipper.

Other features and advantages of the invention will be apparent from the following description, the accompanying drawing and the appended claims.

BRIEF DESCRIPTION OF THE DRAWING FIG. 3 is a fragmentary view taken generally on the 7 line 33 of FIG. 2; and

FIG. 4 is a fragmentary section taken generally on the line 4-4 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, a rotary chipper 10 is generally constructed as shown in the above Fish et al. U.S. Pat. No. 2,756,788. That is, the chipper 10 includes a driven rotor incorporating a disk-like head 12 which has a plurality of circumferentially spaced radially extending openings 13. A chipping knife 14 is mounted on the head adjacent each opening 13, and the head 12 is enclosed within a housing 15 having an inlet opening 16. An anvil 18 extends into the opening 16 and has an upper flat horizontal surface 19 extending to the path of the cutting edges of the knives 14. In the same manner as disclosed in the above patent, scrap sheets of veneer are fed to the chipper l0 and across the anvil surface 19 by a conveyor including an endless belt 22 directed around a guide roll 23 positioned adjacent the anvil 18. As the material is delivered to the anvil 18 by the upper horizontal run of the conveyor belt 22, the material contacts a smaller diameter speed up roller 25 which is driven by a motor 26 so that the peripheral speed of the roll 25 is substantially greater than the speed of the belt 22 to assist in feeding the scrap veneer material into the chipper 10.

A stationary shaft 28 is spaced above the upper run of the conveyor belt 22 and extends laterally between the vertical side walls (not shown) of the main support frame generally indicated at 30. A housing 31 is pivotally mounted on the shaft 28 and covers a feed drum 32 which is mounted on a shaft 33 rotatably supported by bearings 34 secured to the housing 29. The feed drum 32 has a series of circumferentially spaced and axially extending ribs 35 which are adapted to engage the uppermost sheet of the mat of veneer material being carried by the conveyor belt 22. The feed drum 32 is driven by a motor 36 at a speed correlated to that of the conveyor belt 22.

A pneumatic cylinder 38 is supported by the main frame 30 and includes a piston rod 39 which is pivotally connected to the housing 31. The pressure within the cylinder 38 is controlled according to the pressure desired between the feed drum ribs 35 and the mat of veneer strips or material on the conveyor belt 22. A set of ball-like stops 40 are mounted on the main frame 30 and are adapted to receive sockets 41 secured to the housing 31 when the feed drum 32 is located in its lowermost position as shown in FIG. 1.

A segmented holddown or press roll 45 is positioned directly above the conveyor guide roll 23 and is mounted on a shaft 46 which is rotatably supported by bearings secured to a pair of parallel spaced support arms 48 pivotally mounted on the stationary cross shaft 28. The shaft 46 is driven by the motor 36 at a speed correlated to the speed of the shaft 33 supporting the feed drum 32. As shown in FIG. 3, the axially spaced segment 51 of the feed roll 45 define a series of axially spaced circumferential grooves 52.

In accordance with the present invention, a series of axially extending resilient ribs 54 (FIG. 2) are spaced circumferentially around the outer cylindrical surface of each press roll segment 51. Preferably, each rib 54 is molded of a hard rubber material and is bonded to the outer cylindrical surface of the roll segment by a suitable cement. As illustrated in FIG. 2, the ribs 54 normally engage the conveyor belt 22 as the belt is directed onto the guide roll 23. The press roll 45 is also supported in its lowermost position with the ribs 54 contacting the conveyor belt 22, by a set of resilient shock absorbing rubber blocks 56 which are mounted on the main frame 30 and form stops for the roll support arms 48 when the arms drop to their lowermost positions as shown in FIG. 1.

A series of formed rod-like fingers 60 are spaced laterally above the conveyor belt 22, and the rearward end portion of each finger 60 is rigidly secured to an inverted U-shaped fitting 62 which is rotatably mounted on the stationary cross shaft 28. Preferably, each of the fingers 60 is formed from either fiber glass or a non-ferrous metal such as aluminum and includes a curved intermediate portion 63 which extend through an aligned corresponding groove 52 within the segmented press roll 45, in a manner similar to that shown in the above Fish et al. patent.

The forward end portion 64 of each finger 60 slopes downwardly toward the upper surface 19 of the anvil l8 and carries a generally flat blade-like tip portion 65 having a width substantially wider than the end portion 64 of the fingers 60. As illustrated in FIG. 2, the forward edge of each of the tip portions 65, form a line contact with the anvil 18 across the full width of the tip portion. Each of the top portions 65 include a pair of rearwardly projecting and upwardly sloping ears 67 which are spaced on opposite sides of the finger end portion 64 and are used to guide the veneer underneath the tip portion 65.

A strip 68 (FIG. 2) of flexible belt material extends laterally across the upper surface of the fingers 60 adjacent the supporting shaft 28, and a resilient hollow air spring or bag 70 overlies the belt strip 68. An air valve fitting 72 is mounted on the air bag 70 and provides for inflating the air bag to a selected pressure. Positioned above the air bag 70 is a weight member 75 which includes a laterally extending platform 76 supported on opposite ends by a pair of arms 78 secured to corresponding sleeves 79 rotatably mounted on the cross shaft 28. The weight member 75 also includes a plurality of weight sections or elements 80 which are stacked on the platform 76. The number of the weight elements 80 is selected according to the desired upward force required to lift the weight member 75 from a resilient stop 82 and to pivot the weight member about the axis of the shaft 28.

In operation, as mats of scrap veneer strips or sheets are fed toward the chipper 10 by the upper run of the conveyor belt 22 and the feed drum 32, the strips pass under the driven press roll 45 and are engaged by the rubber ribs 54 on the outer surface of the press roll. As the strips are fed across the anvil 18 and into the chipper 10, the fingers 60 are elevated or pivoted upwardly about the axis of the shaft 28, thereby'compressing the air bag 70 and increasing the downward holddown force exerted on the veneer sheets by the tip portions 65 of the fingers. If the height of the mat of veneer being fed under the fingers 60, increases beyond the predetermined level, the upward force acting on the fingers is transferred through the air bag to the weight member 75, causing the weight member to be lifted from the resilient support 82. Thus the weight member 75 controls the maximum holddown pressure exerted by the tip portions 65 of the fingers 60.

From the drawing and the above description, it is apparent that a veneer feeding and holddown mechanism constructed in accordance with the invention, provides several desirable features and advantages. For exampie, the air bag 70 provides for accommodating variations in feeding conditions. That is, if a wad of veneer has a width which is only sufficient to raise one of the fingers 60 as illustrated in FIG. 4, the downward biasing pressure exerted by the one finger is substantially lower than if all of the fingers were lifted to the same height by a full width mat of veneer of the same thickness. Thus the lesser the width of the mat of veneer, the lesser the holddown force exerted by the fingers 60, which is consistent with the forces required to minimize rebounding of the veneer mat after each cutting operation. The air bag 70 also provides a cushioning effect which helps to dampen bouncing of the fingers with the rebounding of the veneer mat.

As mentioned above, when the fingers 60 raise to a predetermined elevation, the weight member '75 is lifted so that the fingers do not exert any greater force even if they are raised higher by a thicker mat of veneer. The maximum holddown force is thus determined by the number of weight segments 80 which are mounted on the platform of the weight member 75, and the height at which the fingers begin to lift the weight member 75, is determined by the pressure within the air bag 70, which is selected by the volume of air supplied to the bag through the valve fitting 72.

The width of the tip portions 65 of the holddown fingers 60, also provides an important feature. That is, the substantially greater width of the tip portions 65 relative to the width of the finger portions 64, provides for a more continuous holddown force across the full width of the veneer mat and thereby significantly reduces the splitting of the veneer. This results in minimizing the formation of undesirable long chips and thin pin chips. Thus by changing the number of the weight elements 80 on the weight member 75 and by adjusting the air pressure within the air bag 70, the holddown characteristics of the fingers 60, can be selected to provide for optimum feeding of the veneer material into the chipper 10. The air bag 70 and the resilient ribs 54 on the press roll 45 also cooperate to eliminate high shock loads on the veneer material as well as on the feed conveyor belt 22.

While the form of apparatus herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. In apparatus for chipping multiple pieces of scrap veneer and like sheet material, and including power operated knife means supported for rotation adjacent an anvil, a conveyor for feeding the material across the anvil and into said knife means, a plurality of generally parallel spaced fingers having tip portions positioned for urging the material against said anvil during the cutting of the material by said knife means, and means supporting said fingers for upward movement of said tip portions relative to said anvil for accommodating mats of material of various thicknesses being fed by said conveyor, the improvement comprising means including an elongated flexible air bag extending laterally across said fingers for resiliently biasing the upward movement of each said finger, and means for limiting the maximum pressure exerted by said biasing means on each said finger when said finger reaches a predetermined height above said anvil.

2. Apparatus as defined in claim 1 comprising means for adjusting the air pressure within said bag.

3. Apparatus as defined in claim 1 wherein said pressure limiting means comprise a weight member positioned above said biasing means and supported to be lifted in response to raising of said fingers above a predetermined height.

4. Apparatus as defined in claim 3 including a shaft supporting said fingers for pivotal movement, and means pivotally mounted on said shaft for guiding the upward movement of said weight member.

5. Apparatus as defined in claim 1 including a blade member mounted on said tip portion of each said finger and having a generally flat surface substantially wider than said finger to provide a substantially continuous holddown pressure on the material across said anvil.

6. Apparatus as defined in claim 5 including a press roll positioned for rotation above said conveyor and having means defining a plurality of axially spaced circumferential grooves for receiving said fingers, and means supporting said press roll for generally vertical movement relative to said conveyor said blade portions of said fingers being located above said anvil and between said press roll and said knife means.

7. Apparatus as defined in claim 1 including a press roll positioned for rotation above said conveyor and having means defining a plurality of axially spaced circumferentlal grooves Wl'llCll receive said fingers, means supporting said press roll for generally vertical movement relative to said conveyor, and a plurality of circumferentially spaced resilient ribs secured to the outer surface of said press roll.

8. ln apparatus for chipping multiple pieces of scrap veneer and like sheet material, and including power operated knife means supported for rotation adjacent an anvil, a conveyor for feeding the material across the anvil and into said knife means, a plurality of generally parallel spaced fingers having tip portions positioned for urging the material against said anvil during the chipping operation, and means supporting said fingers for upward movement of said tip portions relative to said anvil for accommodating mats of material of various thicknesses being fed by said conveyor, the improvement comprising an air bag overlying said fingers resiliently biasing the upward movement of each said finger, a weight member overlying said air bag, and means supporting said weight member to be lifted in response to said fingers reaching a predetermined height above said anvil. 

1. In apparatus for chipping multiple pieces of scrap veneer and like sheet material, and including power operated knife means supported for rotation adjacent an anvil, a conveyor for feeding the material across the anvil and into said knife means, a plurality of generally parallel spaced fingers having tip portions positioned for urging the material against said anvil during the cutting of the material by said knife means, and means supporting said fingers for upward movement of said tip portions relative to said anvil for accommodating mats of material of various thicknesses being fed by said conveyor, the improvement comprising means including an elongated flexible air bag extending laterally across said fingers for resiliently biasing the upward movement of each said finger, and means for limiting the maximum pressure exerted by said biasing means on each said finger when said finger reaches a predetermined height above said anvil.
 2. Apparatus as defined in claim 1 comprising means for adjusting the air pressure within said bag.
 3. Apparatus as defined in claim 1 wherein said pressure limiting means comprise a weight member positioned above said biasing means and supported to be lifted in response to raising of said fingers above a predetermined height.
 4. Apparatus as defined in claim 3 including a shaft supporting said fingers for pivotal movement, and means pivotally mounted on said shaft for guiding the upward movement of said weight member.
 5. Apparatus as defined in claim 1 including a blade member mounted on said tip portion of each said finger and having a generally flat surface substantially wider than said finger to provide a substantially continuous holddown pressure on the material across said anvil.
 6. Apparatus as defined in claim 5 including a press roll positioned for rotation above said conveyor and having means defining a plurality of axially spaced circumferential grooves for receiving said fingers, and means supporting said press roll for generally vertical movement relative to said conveyor said blade portions of said fingers being located above said anvil and between said press roll and said knife means.
 7. Apparatus as defined in claim 1 including a press roll positioned for rotation above said conveyor and having means defining a plurality of axially spaced circumferential grooves which receive said fingers, means supporting said press roll for generally vertical movement relative to said conveyor, and a plurality of circumferentially spaced resilient ribs secured to the outer surface of said press roll.
 8. In apparatus for chipping multiple pieces of scrap veneer and like sheet material, and including power operated knife means supported for rotation adjacent an anvil, a conveyor for feeding the material across the anvil and into said knife means, a plurality of generally parallel spaced fingers having tip portions positioned for urging the material against said anvil during the chipping operation, and means supporting said fingers for upward movement of said tip portions relative to said anvil for accommodating mats of material of various thicknesses being fed by said conveyor, the improvement comprising an air bag overlying said fingers resiliently biasing the upward movement of each said finger, a weight member overlying said air bag, and means supporting said weight member to be lifted in response to said fingers reaching a predetermined height above said anvil. 